Heterostructure Lasers, Part A: Fundamental Principles deals with the fundamental principles, preparation, and operating characteristics of heterostructure lasers. Each major topic is introduced along with the basic laws that govern the observed phenomena. The expressions relevant to heterostructure lasers are derived from the basic laws, and realistic numerical examples based on the GaAs-AlxGa1-xAs heterostructure are given. This book is comprised of four chapters and begins with a discussion on some of the early studies of injection lasers and an overview of the fundamental concepts of heterostructure lasers. Stimulated emission and room temperature continuous-wave operation with injection lasers are described, together with the fundamentals of waveguiding, gain, and carrier confinement in heterostructures. Optical fields and wave propagation are considered, along with slab-electric waveguides; the relationships between absorption, stimulated emission, and spontaneous emission; optical absorption and emission rates in semiconductors; and electrical properties of heterojunctions. This monograph will be of interest to physicists.